Rotary impact tool

ABSTRACT

A rotary impact tool, especially an impact wrench, having a hammer located in a rotatable guide housing and connected to the latter for rotation therewith and axially reciprocatable with respect thereto between an active and an inactive position. An anvil is located forwardly of the hammer to be rotated by the latter in the active position thereof. The guide housing and therewith the hammer are rotated by drive means which include a central stator and a hollow cylindrical rotor connected with the guide housing for rotation.

Hess Sept. 30, 1975 [54] ROTARY IMPACT TOOL 3,672,797 6/1972 Gerlach etal. 4l8/l75 [75] Inventor: Johann Hess, Stuttgart, Germany FOREIGNPATENTS OR APPLICATIONS [73] Assigneez Robert Bosch GJHJLH Stuttgart,2,124,149 5/1971 Germany 173/93 Germany 43-24254 1/1965 Japan l73/93.6

[22] Filed: 1974 Primary Examiner-James A. Leppink [21] APPL NOJ 450,486Attorney, Agent, or FirmMichael S. Striker [30] Foreign ApplicationPriority Data [57] ABSTRACT Mar 17 1973 Germany 2313402 A rotary impacttool, especially an impact wrench, I having a hammer located in arotatable guide housing [52] U S Cl 173/93, 81/52 3 and connected to thelatter for rotation therewith and [51] Ezl) 15/60 axially reciprocatablewith respect thereto between an [58 1 Field of 173/93 935 active and aninactive position. An anvil is located for- V 1 wardly of the hammer tobe rotated by the latter in the active position thereof. The guidehousing and there- [56] References Cited with the hammer are rotated bydrive means which include a central stator and a hollow cylindricalrotor UNITED STATES PATENTS connected with the guide housing forrotation. 3.5 6.769 6/1970 Korhonen 418/175 3.639.092 2/1972 Sauvaget418/175 10 Clams, 2 Drawlng Flgures 1 i L1G B '8 1o, 11 1 1 a 1- as I Iii t lV/ V 5 if r 7 a I k I lo I 26 19 0i] 9 I v 31 \V W l'f' L2 9 21. 1j r- 21,311 5 4 A 3a ,1 B 35 i t 2 I x 20 14 6 15 131 W k 12 7A 32 37 asUS. Patent Sept. 30,1975 sheet 2 of2 3,908,768

1 ROTARY IMPACT TOOL BACKGROUND OF THE INVENTION The present inventionrelates to a rotary impact tool, especially an impact wrench, with animpact'mechanism comprising a coaxially arranged anvil and ham- SUMMARYOF THE INVENTION It is an object of the present invention to provide arotary impact tool of the aforementioned kind in which the active massof the striking mechanism is increased by the mass of the rotor.

It is a further object of the present invention to provide a rotaryimpact tool of the aforementioned kind which is very compact inconstruction so that it may be handled conveniently by the operator andso that it may be manufactured at reasonable cost and will stand upproperly under extended use.

With these and other objects in view, which will become apparent as thedescription proceeds, the rotary impact tool according to the presentinvention mainly comprises a tool housing, drive means in the toolhousing and comprising a stator and a rotor surrounding the stator, apot-shaped guide housing in thetool housing and connected to the rotorfor rotation therewith, with the bottom wall of the guide housingrotatably supported on the stator, a hammer arranged in the guidehousing for reciprocating movement relative thereto,

and cooperating means on the guide housing and the hammer for connectingthe hammer with the guide housing for rotation therewith permittingaxial movement of the hammer relative to the guide housing.

The aforementioned cooperating means preferably comprise an internalgearing on the guide housing and an external gearing on the hammermeshing with the internal gearing.

An especially advantageous arrangement is derived when the end of therotor facing the impact mechanism is provided with a hollow cylindricalprojection which extends over the outer surface of the guide housing andis supported on the latter.

The drive means is preferably constituted by a vane -motor operated bycompressed air and the hollow cylindrical rotor defines with the statorof the vane motor The novel features which are considered ascharacteristic for the invention are set forth in particular in theappended claims. The invention itself, however, both as to itsconstruction and its method of operation,

together with additional objects and advantages thereof, will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

, BRIEF DESCRIPTION OF THE DRAWING:

FIG. 1 is a side view of the impact tool partially sectioned along itsaxis; and

FIG. 2 is a cross-section taken along the lines 2-2 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

Referring now to the drawing, it will be seen that the impact wrenchaccording to the present invention has a substantially drumed-shapedtool housing 1 which is provided at its rear portion with adownwardlyextending handle 2. The drive for the impact mechanism of the impactwrench is located in the rear portion of the housing 1 and the drive ispreferably constituted by a vane motor operated by compressed air. Theimpact mechanism of the wrench is located in the front part of thehousing.

The vane motor has an outer tubular rotor 3 which has an inner annular,preferably cylindrical, eccentric reaction surface 6 which surroundsasmall stator 4 which is located coaxially with the rotor. Stator 4 hascircumferentially spaced radially extending slots'4a in which vanes 5are guided for radial reciprocating movement; Springs4b in the bottomportions of the slots 4a, urge the vanes 5 outwardly so that the ends ofthe vanes 5 are in contact with the eccentric reaction surface 6duringrotation of the rotor- 3. The crescentshaped cavity between the annularsurface 6 and the outer surface 40 of the rotor is divided by the vanes5 into working chambers 5a which expand on one side.of a verticaldead-center plane, and contract on the other side thereof to receive anddischarge fluid, respectively. The outer surface 40 of the stator is incontact with the inner reaction surface 6 of the rotor along an axialline'located in the dead-center plane of the apparatus which-also passesthrough the axis of the'rotor 3. The housing portion 1a which closes thetubular housing 1 has a threaded axial bore 31 into which the thread ofan extension 3a of the stator 4 is threaded. In this" manner, thecentral stator 4 is mounted at oneend the housing portion la.

The axial ends of the tubular rotor 3 are provided with radial rotor endwalls 7 and 7a secured by screws, not shown, to the tubular rotor 3. Theaxial distance between the confronting faces of the rotor end walls 7and 7a correspond to the effective axial length of the stator 4 andofthe vane 6, a small amount of clearance being provided.

i The rotor end wall has a central opening through which the extension312 of the stator 4 projects, forming with the rotor end wall 70 anannular space in which a ball-bearing 32 is located so that the rotor 3is supported at the respective end for rotation on the extension 3a ofthe stator. The other end of the stator 4 has a cylindrical extension 8projecting beyond the other rotor end wall 7, and carrying'aballbearing9 on which the bottom wall 10 of a pot-shaped hammer guide housing 13 ismounted. The cylindrical outer surface of the bottom wall 10 is closelyfitted at 11 into the inner surface of a hollow cylindrical extension l2 of the rotor 3 and thus supports the latter. A spline ,17 formedwithin the free end of the hollow cylindrical extension 12 and on theouter surfaceof the bottom 10 ofthe. guide housing 13 connects thelatter for rotation with the rotor 3. The guide housing 13 is turnablymounted by means of a needle bearing 13 in the housing 1.

The suply of compressed air to the vane motor takes place through themain valve in the grip portion 2 of the housing operated by a button 33.The two-way shifting valve 34, only schematically shown, supplies thepressure air either to conduit 35 or to conduit 36, depending on thedesired direction of rotation of the rotor 3.

Assuming now that the pressure air is guided from the valve 34 into theinlet conduit 36, the pressure air flows into a circular channel 37closed by circular end face of the rotor end wall 7a, but being swept byan axial conduit 38 in the rotor end wall 7a during rotation of therotor 3. The air under pressure flows from the pressure conduit 38 intoa recess 39 (FIG. 2) of the eccentric reaction surface 6 of the rotor.The recess 39 has a rounded end 39' adjacent the dead-center plane ofthe vanes 5, as best seen in FIG. 2, and is generally arcuate, wideningtoward the end of the rotor; The recess 39 is located at the highpressure side formed by expanding working chambers 5a and extends overabout one-quarter of the circumference of the inner annular reactionsurface 6 of the rotor. Particularly, the deepest part of the recess 39has an axial length corresponding to about 30 percent of the axiallength of the reaction surface 6, so that the outer edges of the vanes 5still contact 70 percent of the maximum available surface of thereaction surface 6.

At the low pressure side of the vane motor, another recess 40 isprovided at the other end of rotor 3, which is mirror-symmetrical to thedead-center plane, and from which the air is discharged. The roundedends 39, 40' of the recesses 39, 40 are angularly displaced at an angleof about 40, symmetrically to the deadcenter plane of the vanes 5.Pressure air from the recess 40 enters a conduit portion 41a,communicating with the radial conduit 41 having an annular port 42 whichis swept by a conduit portion 43a of a central axially extending conduit43 which passes along the axis of the stator 4 into the dischargeconduit 35 which is con-- transform the energy of the suppliedcompressed air into a torque acting on the rotor 3. During continuousrotation, the working chambers 5a are contracted so that the lowpressure air is discharged, as explained. the arrangement of the conduitfor the pressure air and discharged air has the advantageous result ofreducing and damping the noise produced by the apparatus.

The hammer guide housing 13 is pot-shaped and is provided at its innersurface therefor with an axially extending internal gearing 14. Theinternal gearing 14 meshes with an external gearing 15 provided on theouter surface of a hammer 16 located in the interior of the hammer guidehousing 13 so that the hammer 16 is constrained to rotate with the guidehousing 13 during rotation of the latter, while being axially movablewith respect thereto. The hammer 16 carries at a front face thereofcircumferentially spaced impact cocks 18 which are adapted to cooperatewith corresponding impact cocks 19 on an anvil 20 located forwardly ofthe hammer 16. The anvil 20 is turnably mounted in a bearing in a frontend portion of the housing 1 and projects with a tool head 21 of squareor polygonal cross-section beyond the housing on which a tool, forinstance a socket wrench may bemounted.

A control shaft 22 is coaxially arranged with the impact mechanismformed by the hammer l6 and the anvil 20 and the control shaft 22 isfixed to the anvil 20 for rotation therewith. The control shaft has atits end distant from the anvil 20 a collar 23 with a circumferen'tiallyextending axially rising and falling cam face 24 engaged by a ball 25which is guided in an annular cutout and an end face of the hammer 16which faces the can face 24 of the collar 23. On the face thereofopposite the cam face 24, the collar 23 abuts against an axial rollerbearing 26 on the bottom wall 10 of the guide housing 13. An extension27 of the control shaft 22 is mounted in a slide bearing 28 provided inthe bottom wall 10 of the guide housing 13. A compression spring 29located in a space about the control shaft 22 abuts with one end againstthe anvil 20 and with the other end against the hammer 16. Thecompression spring'29 biases the hammer 16 to a position in which thecocks 18 on the hammer 16 are out of engagement with the cocks 19 on theanvil 20. At the same time, the spring therewith the hammer 16 arerotated. Thereby, the

control shaft 22 connected to the anvil 20 for rotation is taken alongthrough the friction between the hammer l6 and the ball 25, on the onehand and the'ball and the cam surface 24 on the other hand. At the sametime part of the turning moment imparted to the hammer 16 by the vanemotor is also transmitted through the compression spring 29 to the anvil20. In this way the anvil 20 it rotated together with the hammer 16. Ifthe anvil 20 is now arrested by outside forces, for instance if the nutturned thereby encounters resistance, then the friction connectionbetween hammer and anvil will be overcome so that the hammer 16 willrotate relative to the anvil 20 and the control shaft 22 connected tothe latter. Thereby, the ball 20 will move on the rising portion of thecam face 24 and move thereby the hammer 16 axially towards the left toan active position, as viewed in FIG. 1, so that the cogs 18 and 19 willengage with each other with an impact to thereby tighten the nut. Sincethe cam face 24 drops again, the cocks l8 and 19 will be brought againout of engagement, where-' after the cycle will be repeated until theturning resistance imparted from outside onto the anvil and the toolconnected thereto is overcome.

The described construction of the rotor 3 which is connected to theguide housing 13 for rotation is characterized by a very large inertiamoment due to the relative large radial distance of the rotating massesfrom the axis of the tool.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofrotary impact tools differing from the types described above.

While the invention has been illustrated and described as embodied in arotary impact tool, especially an impact wrench, it is not intended tobe limited to the details shown, since various modifications andstructural changes may be made without departing in any way from thespirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can be applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patentisset forth in the appended claims:

1. In a rotary impact tool, especially an impact wrench, a combinationcomprising a tool housing; drive means in said housing and comprising acentral stator and a tubular rotor surrounding said stator; a potshapedguide housing in said tool housing and connected to the rotor forrotation therewith, said potshaped guide housing having a bottom wallfacing said drive means and being rotatably supported on said centralstator; a hammer arranged in said guide housing for reciprocatingmovement relative thereto; and cooperating means on said guide housingand said hammer for connecting the hammer with the guide housing forrotation therewith while permitting axial movement of said hammerrelative to said guide housing.

I 2. A combination as defined in claim 1, wherein said cooperating meanscomprise an internal gearing on said guide housing and an externalgearing on said hammer meshing with said internal gearing.

3. A combination as defined in claim 1, wherein said drive means isconstituted by a vane motor operated by compressed air, said hollowcylindrical rotor defining with said stator a working space, said statorbeing provided with a plurality of radially extending slots, andincluding a plurality of vanes closely guided in said slots and dividingsaid working space in a plurality of working chambers.

4. A combination as defined in claim 1, wherein said hammer isreciprocatable in said guide housing between an active and an inactiveposition, and including an anvil turnable mounted in said housingadjacent that end of said hammer which is distant fromsaid drive meansand cooperating with said hammer to be turned by the latter in theactive position of the latter.

5. A combination as defined in claim 4, and including control means forreciprocating said hammer during rotation thereof with said guidehousing, said control means comprising a control shaft coaxially fixedto said 'anvil for rotation therewith, a collar fixed to said shaft andprovided with an axially rising and falling cam face facing the otherend of said hammer, a ball riding on 'said cam face, and spring meansfor pressing said other tend of said hammer against said ball.

6. In a rotary tool, especially an impact wrench, a ;combinationcomprising a tool housing; drive means in said housing and comprising astator and a tubular rotor surrounding said stator; a pot-shaped guidehousing in said too] housing, said pot-shaped guide housing having abottom wall facing said drive means and being rotatably supported onsaid stator; a hollow cylindrical projection on said rotor extendingover said guide housing to support said rotor on said guide housing; ahammer arranged in said guide housing for reciprocating movementrelative thereto; and cooperating means on said guide housing and saidhammer for connecting the hammer with the guide housing for rotationtherewith while permitting axial movement of said hammer relative tosaid guide housing.

7. A combination as defined in claim 6, wherein said bottom wall of saidguide housing has a cylindrical outer surface closely fitted in theinner surface of said hollow cylindrical projection.

8. A combination as defined in claim 6, and including a spline in theregion of the free end of said projection for connecting said rotor withsaid guide housing.

9. In a rotary impact tool, especially an impact wrench, a combinationcomprising a tool housing; drive means in said housing and comprising astator and a tubular rotor surrounding said stator; a pot-shaped guidehousing in said tool housing and connected to said rotor for rotationtherewith, said pot-shaped guide housing having a bottom wall facingsaid drive means and being rotatably supported on said stator; a hammerarranged in said guide housing for reciprocating movement relativethereto between an active and an inactive position; an anvil turnablymounted on said tool housing adjacent that end of said hammer which isdistant from said drive means and cooperating with said hammer to beturned by the latter in said active position; cooperating means on saidguide housing and said hammer for connecting said hammer with said guidehousing for rotation therewith while permitting axial movement of saidhammer relative to said guide housing; control means for reciprocatingsaid hammer during rotation thereof with said guide housing; saidcontrol means comprising a control shaft coaxially fixed to said anvilfor rotation therewith, a collar fixed to said shaft and provided withan axially rising and falling cam face facing the other end of saidhammer, a ball riding on said cam face, and spring means for pressingsaid other end of said hammer against said ball, an axial thrustsbearing between the side of said collar facing away from said cam faceand the bottom wall of said guide housing; and a sleeve bearing in saidbottom wall of said guide housing, said control shaft having anextension guided in said sleeve bearing.

10. A combination as defined in claim 9, wherein said axial thrustbearing is a roller bearing.

1. In a rotary impact tool, especially an impact wrench, a combinationcomprising a tool housing; drive means in said housing and comprising acentral stator and a tubular rotor surrounding said stator; a pot-shapedguide housing in said tool housing and connected to the rotor forrotation therewith, said pot-shaped guide housing having a bottom wallfacing said drive means and being rotatably supported on said centralstator; a hammer arranged in said guide housing for reciprocatingmovement relative thereto; and cooperating means on said guide housingand said hammer for connecting the hammer with the guide housing forrotation therewith while permitting axial movement of said hammerrelative to said guide housing.
 2. A combination as defined in claim 1,wherein said cooperating means comprise an internAl gearing on saidguide housing and an external gearing on said hammer meshing with saidinternal gearing.
 3. A combination as defined in claim 1, wherein saiddrive means is constituted by a vane motor operated by compressed air,said hollow cylindrical rotor defining with said stator a working space,said stator being provided with a plurality of radially extending slots,and including a plurality of vanes closely guided in said slots anddividing said working space in a plurality of working chambers.
 4. Acombination as defined in claim 1, wherein said hammer is reciprocatablein said guide housing between an active and an inactive position, andincluding an anvil turnable mounted in said housing adjacent that end ofsaid hammer which is distant from said drive means and cooperating withsaid hammer to be turned by the latter in the active position of thelatter.
 5. A combination as defined in claim 4, and including controlmeans for reciprocating said hammer during rotation thereof with saidguide housing, said control means comprising a control shaft coaxiallyfixed to said anvil for rotation therewith, a collar fixed to said shaftand provided with an axially rising and falling cam face facing theother end of said hammer, a ball riding on said cam face, and springmeans for pressing said other end of said hammer against said ball. 6.In a rotary tool, especially an impact wrench, a combination comprisinga tool housing; drive means in said housing and comprising a stator anda tubular rotor surrounding said stator; a pot-shaped guide housing insaid tool housing, said pot-shaped guide housing having a bottom wallfacing said drive means and being rotatably supported on said stator; ahollow cylindrical projection on said rotor extending over said guidehousing to support said rotor on said guide housing; a hammer arrangedin said guide housing for reciprocating movement relative thereto; andcooperating means on said guide housing and said hammer for connectingthe hammer with the guide housing for rotation therewith whilepermitting axial movement of said hammer relative to said guide housing.7. A combination as defined in claim 6, wherein said bottom wall of saidguide housing has a cylindrical outer surface closely fitted in theinner surface of said hollow cylindrical projection.
 8. A combination asdefined in claim 6, and including a spline in the region of the free endof said projection for connecting said rotor with said guide housing. 9.In a rotary impact tool, especially an impact wrench, a combinationcomprising a tool housing; drive means in said housing and comprising astator and a tubular rotor surrounding said stator; a pot-shaped guidehousing in said tool housing and connected to said rotor for rotationtherewith, said pot-shaped guide housing having a bottom wall facingsaid drive means and being rotatably supported on said stator; a hammerarranged in said guide housing for reciprocating movement relativethereto between an active and an inactive position; an anvil turnablymounted on said tool housing adjacent that end of said hammer which isdistant from said drive means and cooperating with said hammer to beturned by the latter in said active position; cooperating means on saidguide housing and said hammer for connecting said hammer with said guidehousing for rotation therewith while permitting axial movement of saidhammer relative to said guide housing; control means for reciprocatingsaid hammer during rotation thereof with said guide housing; saidcontrol means comprising a control shaft coaxially fixed to said anvilfor rotation therewith, a collar fixed to said shaft and provided withan axially rising and falling cam face facing the other end of saidhammer, a ball riding on said cam face, and spring means for pressingsaid other end of said hammer against said ball, an axial thrustsbearing between the side of said collar facing away from said cam faceand the bottom wall of said guide housing; anD a sleeve bearing in saidbottom wall of said guide housing, said control shaft having anextension guided in said sleeve bearing.
 10. A combination as defined inclaim 9, wherein said axial thrust bearing is a roller bearing.